Bud-grafting success inAcer platanoides‘Crimson King‘ related to root growth

Abstract

SummarySummer bud-grafting (budding) of the red-leaved scion ‘Crimson King’ onto Acer platanoides rootstocks is unreliable. Typically, the rootstock produces copious callus from the incision in the stem, but the scion bud-chip fails to survive and complete the union. Percentage bud-take was consistently low when rootstocks were grown and budded in 2 litre containers (e.g. 33%), moderately high, but below commercially acceptable levels, when grown in a light sandy loam soil in the field (e.g. 77%), and often very high when grown in deep sand beds (e.g. 100%). The growth of larger structural roots was in the order pot < field soil < sand beds, and confining the roots of field-grown rootstocks in porous mesh bags reduced bud-take from 79 to 13% averaged over three sites. Increasing shoot growth by growing rootstocks in a polythene house did not improve bud-take, but increasing the pot size from 2.0 to 7.5 litres did so. Extensive root growth appears to be one of a number of factors determining bud-take, which was increased further by treating the scionwood and rootstocks with a mixture of Benlate and Rovral fungicides prior to budding. These results are discussed in terms of the need to maintain the bud-chip in a viable condition during the union forming process.